Provided is an annular spacer to be disposed such that a main surface of the spacer is in contact with a magnetic disk in a hard disk drive device, the spacer including two main surfacesi an inner circumferential surfacei and an outer circumferential surface, in which a chamfered surface is present between the outer circumferential surface and each of the two main surfaces, and at least a portion of an outer circumferential region of at least one of the two main surfaces includes an inclined region that is inclined toward the other main surface side in a radial direction from a center of the spacer to the outer circumferential surface side